@On1: welcome to the forums! There is no “undo” if you delete a cam. If you have the box, the s/n is on the label. Here’s a helpful hint for future use: make the s/n part of the name of the cam i.e Patio 123-456-789. It comes in handy at times although probably wouldn’t help in this case. I also keep a list of my cams by location and their s/n’s. Good luck!